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[Qemu-devel] [PATCH 08/13] qemu-ga: become_daemon(): reopen standard fds
From: |
Michael Roth |
Subject: |
[Qemu-devel] [PATCH 08/13] qemu-ga: become_daemon(): reopen standard fds to /dev/null |
Date: |
Tue, 15 May 2012 09:48:54 -0500 |
From: Luiz Capitulino <address@hidden>
This fixes a bug where qemu-ga doesn't suspend the guest because it
fails to detect suspend support even when the guest does support
suspend. This happens because of the way qemu-ga fds are managed in
daemon mode.
When starting qemu-ga with --daemon, become_daemon() will close all
standard fds. This will cause qemu-ga to end up with the following
fds (if started with 'qemu-ga --daemon'):
0 -> /dev/vport0p1
3 -> /run/qemu-ga.pid
Then a guest-suspend-* function is issued. They call bios_supports_mode(),
which will call pipe(), and qemu-ga's fd will be:
0 -> /dev/vport0p1
1 -> pipe:[16247]
2 -> pipe:[16247]
3 -> /run/qemu-ga.pid
bios_supports_mode() forks off a child and blocks waiting for the child
to write something to the pipe. The child, however, closes its reading
end of the pipe _and_ reopen all standard fds to /dev/null. This will
cause the child's fds to be:
0 -> /dev/null
1 -> /dev/null
2 -> /dev/null
3 -> /run/qemu-ga.pid
In other words, the child's writing end of the pipe is now /dev/null.
It writes there and exits. The parent process (blocked on read()) will
get an EOF and interpret this as "something unexpected happened in
the child, let's assume the guest doesn't support suspend". And suspend
will fail.
To solve this problem we have to reopen standard fds to /dev/null
in become_daemon(), instead of closing them.
Signed-off-by: Luiz Capitulino <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Signed-off-by: Michael Roth <address@hidden>
---
qemu-ga.c | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/qemu-ga.c b/qemu-ga.c
index 8d53e04..6e7caed 100644
--- a/qemu-ga.c
+++ b/qemu-ga.c
@@ -445,9 +445,9 @@ static void become_daemon(const char *pidfile)
goto fail;
}
- close(STDIN_FILENO);
- close(STDOUT_FILENO);
- close(STDERR_FILENO);
+ reopen_fd_to_null(STDIN_FILENO);
+ reopen_fd_to_null(STDOUT_FILENO);
+ reopen_fd_to_null(STDERR_FILENO);
return;
fail:
--
1.7.4.1
- [Qemu-devel] [PULL] qemu-ga fixes for 1.1, Michael Roth, 2012/05/15
- [Qemu-devel] [PATCH 02/13] qemu-ga: don't warn on no command return, Michael Roth, 2012/05/15
- [Qemu-devel] [PATCH 04/13] qemu-ga: guest-suspend-disk: don't emit a success response, Michael Roth, 2012/05/15
- [Qemu-devel] [PATCH 01/13] qapi: add support for command options, Michael Roth, 2012/05/15
- [Qemu-devel] [PATCH 03/13] qemu-ga: guest-shutdown: don't emit a success response, Michael Roth, 2012/05/15
- [Qemu-devel] [PATCH 05/13] qemu-ga: guest-suspend-ram: don't emit a success response, Michael Roth, 2012/05/15
- [Qemu-devel] [PATCH 12/13] qemu-ga: fix segv after failure to open log file, Michael Roth, 2012/05/15
- [Qemu-devel] [PATCH 06/13] qemu-ga: guest-suspend-hybrid: don't emit a success response, Michael Roth, 2012/05/15
- [Qemu-devel] [PATCH 11/13] qemu-ga: guest-shutdown: use only async-signal-safe functions, Michael Roth, 2012/05/15
- [Qemu-devel] [PATCH 08/13] qemu-ga: become_daemon(): reopen standard fds to /dev/null,
Michael Roth <=
- [Qemu-devel] [PATCH 07/13] qemu-ga: make reopen_fd_to_null() public, Michael Roth, 2012/05/15
- [Qemu-devel] [PATCH 09/13] qemu-ga: guest-suspend: make the API synchronous, Michael Roth, 2012/05/15
- [Qemu-devel] [PATCH 10/13] qemu-ga: guest-shutdown: become synchronous, Michael Roth, 2012/05/15
- [Qemu-devel] [PATCH 13/13] qemu-ga: align versioning with QEMU_VERSION, Michael Roth, 2012/05/15
- Re: [Qemu-devel] [PULL] qemu-ga fixes for 1.1, Luiz Capitulino, 2012/05/21